A Chemical and Microscopic Study of Decayed Earlywood and Latewood of Loblolly Pine Killed by the Southern Pine Beetle

Shamoun F. Shamoun, Michael P. Levi


Chemical and anatomical changes in the wood of loblolly pines (Pinus taeda L.) killed by southern pine beetles (Dendroctonus frontalis Zimm) were examined. The trees had been dead for approximately 20 months, and were harvested near Jacksonville, North Carolina. Decay occurred in both earlywood and latewood although the rate of deterioration was greater in the earlywood. The dominant patterns of decay in earlywood were dissolution of the secondary walls from the lumen outward toward the middle lamella, and finally a total destruction of cell-wall structure. Decay in latewood was characterized by localized dissolution of the secondary walls, and the formation of "soft-rot" type cavities in the S2 layer of the secondary walls. Chemical analysis showed little or no difference in proportions of holocellulose and lignin in earlywood and latewood of sound and beetle-killed wood. One percent NaOH solubility of both earlywood and latewood was significantly greater in beetle-killed wood than in sound wood. These characteristics suggest that the primary fungus responsible for decay may be Peniophora sp., a fungus commonly found in stored southern pine logs. The results indicate that the beetle-killed wood could be used successfully as a furnish for pulp and reconstituted board products.


Decay;chemical analysis;microscopy;loblolly pine;southern pine beetle;earlywood;latewood

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